FI93069C - Frequency generation for extended bandwidth television - Google Patents

Abstract

In a Multiplexed Analog Component (MAC) color television transmission system in which the MAC signal is to be converted at the receiver to a composite color television signal having a 227.5 fH color subcarrier, frequency-generation equipment required at the receiver is simplified, and bandwidth is extended, by selecting the various frequencies in accordance with the following relationship: f0=3f1=3f2=2f4=1365k fH where: f0 is the master clock frequency, f1 is the luminance samping frequency, f2 is the chrominance sampling frequency, f4 is the MAC sampling frequency, fH is the horizontal line frequency, and k is a positive integer greater than 2. f3 is the data clock frequency which is independent of k and remains fixed at its present value. For MAC receivers designed for C, D or C/2 standards, the relationship becomes f0=3f1=6f2=2f4=1296k fH where the symbols have the same meaning as above. f3 is the data clock frequency which is independent of k and fixed at 1296 fH for the present C, D-MAC standards and 648 fH for the present D/2-MAC standards.

Description

93069

This invention is directed to encoding and decoding multiplexed analog-5 component (MAC) color television signals. More particularly, this invention is directed to frequency generation for encoding and decoding MAC color television.

Combined color television signals, as is well known to those skilled in the art, are those in which chrominance information (i.e., color) is carried on an auxiliary carrier and transmitted with luminance information (i.e., brightness). In the United States, color transmissions are made according to the National 15 Television Systems Committee (NTSC) standard. Other combined signals include SECAM, which is used in France, and PAL, which is prevalent elsewhere in Europe.

Figure 1 shows a radio frequency amplitude curve as a function of frequency in which an NTSC signal is amplitude modulated by a radio frequency carrier and filtered for stub band amplitude modulation for terrestrial transmission in accordance with FCC regulations. A typical combined NTSC color television signal is shown and includes a luminance signal 12 and a Kro-minansign signal 14. The signal assumes a nominal 6 MHz radio frequency bandwidth with the image carrier 16 above the lower end of the 1.25 MHz band. The luminance information is amplitude modulated directly over the image carrier 30. The chrominance information is modulated on the color subcarrier 18, which in turn is used to modulate the image carrier, while the audio information is modulated on the subcarrier 20. The color subcarrier has a frequency of 3,579,545 MHz, a standard established by the NTSC. The lower chrominance sideband 35 and portions of the lower luminance sidebands are removed, not transmitted.

93069 2

It has long been found that combined color vision signals have problems with their structure. For example, the co-coverage of chrominance and luminance information in area A leads to problems because the separation of luminance and chrominance is performed by filtering the frequency division multiplexed signal. If complete separation between luminance and chrominance is desired in reception, the necessary filtering will cause some information to be lost in both signals. On the other hand, if none of the 10 information losses can be allowed, the interference between the luminance and chrominance signals must be accepted. In addition, since different parts of the NTSC television signal are transmitted at different frequencies, they are affected differently by the non-uniform amplitude / frequency response that occurs in the transmission, causing the signal to deteriorate. Also, the available color information is severely limited by the small color bandwidth allowed by the choice of color carrier.

The color signal-20 vision signal for multiplexed analog components (MACs) was developed to overcome the problems inherent in combined color television systems. Turning now to Figure 2, an amplitude-time diagram of a MAC video line is shown, and includes line quenching tar (HBI) 22, chrominance information 24, and lu-25 mining information 26 (either or both of which may be time-compressed), the latter separated by a guard interval. , which assists in preventing interference between the two signals.

The MAC color television signal is obtained by generating conventional luminance and chrominance signals (as would be done to achieve a conventional NTSC or other combined color television signal) and sampling and storing these signals separately in memory. Luminance 35 is sampled at the luminance sampling frequency and stored in the luminance memory, while chrominance is sampled at the chrominance sampling frequency and stored

II

3 93069 chrominance memory. The luminance and chromium samples can then be compressed over time by first writing them down at their individual sampling frequencies and reading them from memory at a higher frequency. The Multiplek-5 soy selects either the luminance or chrominance memory at the appropriate time during the active video line for reading, thus creating the MAC signal of Figure 2. If desired, audio samples can be sent during HBI; these are multiplexed (and can be compressed) in the same way as video samples. The simple frequency at which all samples appear in the multiplexed MAC signal is called the MAC sampling frequency.

Various physical embodiments have been developed that implement the MAC format of Figure 2. For example, several MAC formats have been implemented with 3: 2 luminance compression. European C, D and D / 2,625 line systems per frame use a MAC sampling frequency of 20,250 MHz. The B-MAC for both the 625 and 525 line systems per image-20 area uses 1365 fjj as the MAC sampling rate, where fjj is the horizontal scan frequency. In addition, one embodiment uses 14.32 MHz as the MAC sampling rate with 4: 3 luminance compression, and another embodiment uses 21.447 MHz as the MAC sampling frequency with 5: 4 luminance-25 compression.

Disadvantages for all of the above MAC embodiments include both limited luminance and chrominance resolution as well as complexity in developing different clock frequencies in receivers. These disadvantages have been analyzed in the physical embodiment shown below with reference to Table 1.

35 4 93069 TABLE 1 Main clock

Sicmal Frequency fraction Main clock (f0) 42.95 MHZ = 2370 fH 1 5 Luminance sampling (f!) 14.32 MHz = 910 fH 1/3

Chrominance sampling (f2) 7.16 MHz = 455 fH 1/6 Sampling of sound 10 (f3) 0.33 MHz = 21 fH 1/130 MAC (f4) sampling 21.48 MHz = 1365 fH 1/2

Teletext developer (f5) 6.14 MHz = 390 fH 1/7 15 NTSC color subcarrier 3.579545 MHz = 227.5 fH 1/12 (Frequency f3 can also be 0.20 MHz, or 13 fH, which is 1/210 of f0.) 20 System , which combines the embodiment shown in Table 1 as a whole, is discussed in detail in the application serial no. 652,926, filed September 21, 1984, now U.S. Patent No. no. 4,652,903. Lucas' 25 patent is generally assigned to the assignee of the present invention and is incorporated herein by reference.

The Lucas embodiment integrates frequencies (for use as sampling frequencies and for other purposes) that are related so that they can be derived from a simple main clock frequency simply by dividing the integer values. Thus, since no frequency multiplication is included (which would be required if the selected frequency could not be divisible by an integer 35 as the main clock frequency), only a simple phase-locked circuit is required. This feature simplifies the hardware required for the receiver and reduces its cost.

5,93069

The upper frequency of information that can be carried without distortion due to spurious reproduction is limited by half (50%) of the sampling frequency (i.e., the Nyquist ratio). The requirement for an economically feasible set of 5 filters in the receiver further reduces the usable bandwidth to about 40% of the sampling frequency. Thus, for the group of frequencies shown in Table 1, the luminescence frequency response is limited to about 6 MHz, while the chrominance frequency response is limited to about 3 MHz.

10

Two of the aforementioned MAC embodiments have been converted to commercial practice and are described in documents to be published by CCIR, an international community that studies the standardization of television signals for international program exchange. These embodiments are 525-line B-MAC and 625-line B-MAC. C and D / 2 MACs will soon be available in Europe for direct satellite transmission. The receivers are currently in use in a number of countries for 20 transmissions compliant with the B-MAC standard and use in other countries is expected soon. Due to the luminance sampling frequencies used by these standards, these transmissions are inherently limited in resolution, as mentioned above. There is a growing interest in improved resolution for 25 widescreen images and there is a strong desire to extend the performance of these MAC systems, as discussed above, to provide improved resolution for new receivers while maintaining full compatibility with existing MAC receivers in good order. for Enhanced Television (HDTV). These MAC embodiments already provide the transmission and display of both *: widescreen and standard aspect ratio images.

Accordingly, it is an object of the present invention to provide a series of frequencies that offer broader bandwidth capabilities than their predecessors.

It is also an object of the present invention to provide a series of frequencies that increase information transmission capacity while maintaining full compatibility with the B-MAC, C-MAC, D-MAC or D / 2-MAC formats at the corresponding frequency of each.

In accordance with these and other objects of the present invention, the set of frequencies is calculated using the following symbols: 1) All frequencies are generated by an integer division from a reasonably feasible main clock; 2) The absolute frequencies of the master clock, MAC sampling clock, luminance, and Kro-minance sampling clocks may increase, but the absolute frequencies of the audio and data sampling clocks should not be changed; 3) development of 227.5 fj by integer division from the main clock; 4) Development of a teletext clock close to 6 MHz with integer division from the main clock; and 5) The sampling frequency of chrominance, and thus the sampling frequency of luminance 20, must be an integer multiple of 455/4 fjj (minimum inverse of the modification gain).

The set of frequencies selected as part of the present invention is related to the B-MAC as follows (frequencies 25 are determined in terms of fH, thus describing both 525 and 625 line systems):

f0 = 3fx = 6f2 = 2f4 = 1365kfH

where: f0 is the main clock frequency; 30 fi is the luminance sampling frequency; f2 is the chrominance sampling frequency; f4 is the MAC sampling rate; k is a positive integer greater than 2.

35 For C, D, and D / 2 MAC systems, the relationship becomes:

f0 = 3f! = 6f2 = 2f4 = 1296k fH

II

7 93069

I have discovered that the symbols listed above, as well as full compatibility with the Lucas embodiment (B-MAC) and the C, D, and D / 2-MAC embodiments with met-frequency series, where the FG will increase ratios shown in 5 before 1365 f: for B-MAC and 1296 fH for C, D and D / 2-MAC. In addition, given a k value of 3.50, an increase in both luminance and chrominance bandwidth is available. Corresponding increases in bandwidths are available for successive increments of k.

10

Because the audio information follows the combined color television signal, which is eventually distributed to the receiver, the audio samples are included in the MAC color television signal. Therefore, the audio sample rate (f3) is also selected to be divisible equally from the main clock frequency.

If teletext is desired, a signal close to 6 MHz must be generated at the receiver to allow the use of standard teletext dot matrix signal generators. Again, the teletext sampling frequency (f5) should be equally divisible by the master clock.

The invention is implemented in a centrally located encoder that converts a color television signal, including luminance and chrominance, into a MAC color television signal, and a decoder in each receiver that converts the MAC color television signal into a combined color television signal. The signal can then be transmitted over most of its transmission path in a more preferred MAC format.

The encoder receives a television signal comprising separate luminance and chrominance components. These 35 components are sampled in a known manner at a suitable (luminance or chrominance) sampling frequency. The luminance samples are compressed in a 3: 2 ratio by writing them to 8,93069 with f ^ r (luminance sampling frequency) and reading them from memory with f ^ r (MAC sampling frequency). The chrominance samples are compressed in a 3: 1 ratio by reading them into memory with f2 (chrominance sampling frequency) and 5 by reading them from memory with f2. The samples are read alternately from the memories (and combined with any desired signals, such as audio samples) by a multiplexer to produce a MAC color television signal that is transmitted to each receiver.

10

In each receiver, the decoder includes a demultiplexer that separates the various components from the MAC signal. The luminescence and chrominance are removed from the compression by an inverse process to that in which they were compressed.

15 Audio or other information is also regenerated.

In the case of B-MAC, 525 lines / image, chrominance samples are used in a known manner to modulate the 227.5 fH NTSC color support base-20 developed in the decoder. The decompressed luminance samples and the modulated subcarrier are then combined with appropriate synchronization and image blanking information into a combined NTSC color television signal. Similarly, the B-MAC 625 line / image can be code-converted to a PAL signal.

Within HBI, different audio channels can be transmitted using time division multiplexing. Teletext information can also be transmitted in the vertical blanking interval (VBI) in a manner well known in the art. The teletext codes are regenerated at the receiver and input to a character generator which generates alphanumeric characters for display on a television screen.

It is essential in this invention to note that a MAC receiver built for current MAC standards has signal processing circuits and clock frequencies that can handle enhanced MAC signals that are inherently higher resolution to be transmitted by the technique of this invention. Different values of K (a positive integer greater than 2) can be used in the studio to encode higher-resolution MAC video. The new 5 systems would maintain the current standard values for data clock frequencies. Thus, the new MAC receiver and the current MAC receiver will decode the data with the same basic but new MAC receiver to achieve additional resolution for new MAC signal transmissions, there will be 10 suitably wider bandwidth filters before the A / D converter, and will use a series of image processing clock frequencies. is simply and appropriately related to standard MAC clock frequencies, i.e. use an increase in these clock frequencies in either a ratio of 3: 2 for which k = 3, or 4: 2 for which k = 4. An existing MAC receiver, or receivers designed for existing standards, can be considered as members of a group where k = 2 and where the luminance bandwidth can be about 6 MHz. Members of the group where k = 3 can implement a bandwidth of 9 MHz and members where k = 4 can implement a bandwidth of 12 MHz. According to the present invention, any receiver designed to be a member of a group having any of these k values can receive transmissions encoded with any of the positive integer values of 25 k, i. 2,: 3, or 4. Therefore, in the future, when more powerful detectable space transceivers become available, or when terrestrial transmissions of MAC signals begin and coding occurs at k> 2, e.g., 3 or 4, receivers-30 met designed for lower k are able to receive image and sound. Receivers encoded with k = 2, k = 3, or k = 4 can generally regenerate the bandwidth for which MHz = 3 * receiver k. The aforementioned commercially implemented MAC systems have a value of k = 2 and implement a bandwidth of 6 MHz. . An improved MAC system with a value of k = 3 in the receiver can produce a bandwidth of 9 MHz if the 10 93069 transmissions are at the k = 3 or k = 4 level. Conversely, a receiver designed in accordance with the present invention for k = 3 or k = 4 would provide 6 MHz bandwidth for k = 2 transmissions and 9 MHz for k = 3 transmissions and 12 MHz for 5 k = 4 transmissions at both the transmitter and receiver. .

A receiver designed for k = 4 would provide 6 MHz bandwidth when receiving transmissions encoded with k = 2 and 9 MHz for a signal encoded with k = 3, while it would provide 12 MHz with 10 bandwidth when receiving transmissions where k = 4. While receivers designed for the possibility of wider bandwidths (k = 3) could have wider bandwidth filters, they can also be equipped with filters suitable for standard MACs (k = 2). Such filters would improve the signal-to-noise ratio and therefore the image quality.

This future extensibility supports this invention. Essential to this invention is the storage of current data sampling frequencies in any new system. If current systems are defined for k = 2, their data ratios are dependent on k and must remain at their current selected values, where k> 2.

A more complete evaluation of the invention and many of its advantages will be achieved as the invention is better understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 is an amplitude-frequency diagram illustrating a typical NTSC color television signal in a simplified form; Fig. 2 is an amplitude-time diagram of a simple video line of a typical MAC color television signal; Fig. 3 is a diagram of an encoder used with the present invention when used for B-MAC for k = 3; Fig. 4 is a diagram of a circuit used to generate 93069 11 different frequencies required in both the encoder and the B-MAC system decoder; Fig. 5 is a diagram of a decoder used with the present invention for use in a 525-line B-MAC; Fig. 6 is a diagram of a line memory that can be used to compress or decompress luminance or chrominance samples; Fig. 7 is a diagram for B-MACs illustrating the input of signals in and out of the line memory 10 of Fig. 6 from the luminance compression during the removal operation.

A preferred embodiment of the present invention is described using an NTSC color carrier in which a received MAC signal at a receiver is converted to an NTSC signal. However, it should be noted that the present invention is equally applicable to both PAL and SECAM systems, and their corresponding implementation will be readily apparent to those skilled in the art based on the description contained herein.

Table 2 provides the selected frequencies for use in a preferred embodiment of the present invention, where the value of k is selected to be 3. (The frequencies shown in Table 2 are listed as multiples of fH so that both 525 and 625 line systems are described) · «35 12 93069

Table 2 (Main clock fractions in parentheses)

Taaj uus Taaj uus Taaj uus

Signal fB-MAC) (C.D-MAC) (D / 2-MAC ^ 5 Main clock (f0) 4095 fH (1) 388 fH (1) 3888 fH (1)

Luminance sampling (f!) 1365 fH (1/3) 1296 fH (1/3) 1296 fH (1/3)

Chrominance sampling (f2) 682.5 fH (1/6) 648 fH (1/6) 648 fH (1/6) 10 Sound sampling (f3) 21 fH (1/195) 1296 fH (1/3) 648 fH (1 / 6)

MAC

sampling (f4) 2047.5 fH (l / 2) 1944 fH (1/2) 1944 fH (1/2)

Teletext developer (f5) 409.5 fH (1/10) NTSC Color subcarrier 227.5 fy (1/18)

Thus, the present invention can be generalized not only to, but by way of example of, and not limited to, the Lucas 20 embodiment (B-MAC), these European MAC embodiments. The alternative audio sampling frequency for the B-MAC is 13 fjj, or 1/315 of the main clock frequency. There are four audio channels available at 21 fj and six at 13 fH. In the preferred embodiment, the chrominance, MAC, and teletext times are reset one per line during line off.

As shown in the frequency family of Table 2, a 50% increase in both luminance and chrominance bandwidth is achieved compared to the frequencies used in the Lucas embodiment as shown in Table 1 with reference. Corresponding increases in bandwidth are available for successive increases of 1365 fH to the main clock frequency. For example, referring to Table 3 below, a 100% increase in both luminance and chrominance bandwidths relative to the frequencies in Table 1 is achieved.

Il 13 93069

Table 3 (Main clock fractions in parentheses)

Frequency Frequency Frequency

Signal (B-MAC) (C.D-MAC) (D / 2-MACM

5 Main clock (f0) 5460 fH (1) 5184 fH (1) 5184 fH (1)

Luminance sampling (fx) 1820 fH (1/3) 1728 fH (1/3) 1728 fH (1/3)

Chrominance sampling (f2) 910 fH (1/6) 864 fH (1/6) 864 fH (1/6) 10 Sound sampling (f3) 21 fH (1/195) 1296 fH (1/3) 648 fH ( 1/6)

MAC

sampling (f4) 2730 fH (1/2) 2592 fH (1/2) 2592 fH (1/2)

Teletext developer (f5) 390 fH (1/14) NTSC Color subcarrier 227.5 fH (1/24) -

As above, the alternative audio sampling frequency is 13 to 20 fH, or 1/420 of the main clock frequency of the B-MAC.

Figure 3 is a block diagram of the encoder used in this invention (i.e., Table 2). Three color television signals, luminance (Y) and two color difference signals (R-Y and B-Y) 25 are distributed from a conventional color television source and filtered in low-pass filters 100a, 100b and 100c, respectively. The filtered color TV signals are then sampled at an appropriate ratio (e.g., 1365 fn for luminance and 682.5% for each of the chrominance signals for 30 B-MACs where k = 3) in A / D converters 102a, 102b, and 102c.

The vertical filters 104 and 106 provide vertical interpolation of the digital color difference signals R-Y and B-Y in the same order, after which these signals are selected alternately for transmission by the multiplexer 108. In contrast to NTSC television transmission, only one of the two color difference signals is transmitted as chrominance to each MAC.

The digital luminance and chrominance signals are next compressed as described above. The luminance data 5 is written to the luminance memory 110a at 1365 fjj, the luminance sampling frequency, and read from the memory at 2047.5 fjj, the MAC sampling frequency. The chrominance data is written to the chrominance memory 110b at 682.5 fH, the chrominance sampling frequency, and read from the memory 2047.5 10 f jjt ·

While color television signals are being processed, the accompanying audio information is also sampled and compressed for transmission. In the case of B-MAC, four audio channels 15, 1 to 4, are sampled and digitized at a frequency of 21 fn in delta modulators 112a-112d. The four deltamodulated audio channels are then alternately selected for transmission, and compressed to a frequency of 910 fjj, by a multiplexer 114. After compression, the audio is re-sampled at a MAC sampling rate of 20 in the sampling circuit 116. Different audio schemes are characteristic of C-MAC and other D and D / D 2-MAC. B-MAC audio diagrams are given as an example only.

The information, synchronization, timing and teletext transmitted in the VBI are shown in Figure 3 by an arrow marked "VBI". This information is generated in a conventional manner and distributed to multiplexer 118 with a new MAC sampling rate.

30

Multiplexer 118 received four sets of signals, luminance, chrominance, audio and synchronization, timing, and teletext, all occurring at the MAC sampling rate. The multiplexer 118 then combines these signals 35 by selecting them at the appropriate time of incorporation into the MAC video line. After multiplexing, the signals are converted back to analog in D / A converter 120, filtered

II

15 93069 in the low pass filter 122 and is output as a MAC color vision signal.

Figure 4 is a block diagram of a circuit that could be used to generate the various frequencies required in both the encoder and decoder. The master clock 401 comprises a phase locked circuit and generates a master clock signal at a frequency of 4095 fH · This signal is sent to two splitters. Divider 402 divides the master clock signal by two, producing a MAC sampling frequency of 10, which is used by dividers 404 and 405 to produce chrominance and teletext sampling frequencies, respectively. The divider 402 is reset by fjj / 2 pulses during alternating line quenching intervals so that the luminance samples are perpendicular (vertical to vertical). Divider 404 is clocked at 1365 μs and reset with fH / 2 pulses as above for perpendicular chrominance sampling.

These clock frequencies, which are fractions of f ^ rn, are obtained by dividing by two divisors (see Fig. 4) and such divisor must be reset by the fH / 2 pulse during line quenching. The reset function must be applied to the same line quench pulses in both the encoder and the decoder. This can be accomplished by adopting a simple practice.

For example, during the line blanking intervals preceding the even numbered active lines, the reset pulse should perform the reset operation of the binary counters 404 and 407 of Fig. 4. MAC decoders have a circuit for identifying such evenly and oddly numbered lines because there is already such a practice for R-Y, B-Y line transmission. The master clock signal is also sent to splitter 403, producing a new luminance sampling frequency used by splitters 407 and 408 (via splitter 406) to provide NTSC color carrier 525-line-35 to the B-MAC and audio sampling frequencies, respectively. However, other arrangements will be readily apparent to those skilled in the art.

16 93069

Figure 5 is a block diagram of a decoder used in the present invention. The MAC television signal first arrives at the demultiplexer 300, which separates the luminance and chrominance signals as well as the audio, synchronization, timing and teletext information. The luminance signal is distributed to a luminance memory 302 where it is decompressed and then to a low pass filter 304 where it is filtered. The analog luminance signal then goes to output terminal 306. The sampling signals necessary to decompress the luminance are produced in timing generator 308 and fed to luminance memory 302 by two clock controllers 310.

The chrominance signal from the demultiplexer 300 is also removed from the compression in the chrominance memory 312. The separate outputs are provided with two color difference signals which are filtered by low pass filters 314 and then applied to output terminal 306. The required sampling signals are

Signals that do not form luminance or chrominance are also separated from the MAC television signal by demultiplexer 300. These signals include audio, teletext vision, synchronization, and timing information. The audio, teletext and synchronization signals are distributed to the demultiplexer 316 through a second low pass filter 318, while the fixed frequency timing information is distributed to the demultiplexer 316 via a bandpass filter 320.

The demultiplexer 316 separates these signals, supplying audio to the audio demultiplexer 322 and the synchronization and timing signals to the clock and synchronization regeneration circuit 324 and the timing generator 308. The audio information from the demultiplexer 316 is divided 328 clock and synchronization 17 93069 via regeneration circuitry 324. The decoder functions are under the control of a microprocessor 330 that communicates with the clock and synchronization regeneration circuitry 324, the teletext signal generator 328, and the RAM 332 5 along bidirectional busses 334, 338, and 336, respectively.

Output interface 306 receives teletext signals from signal generator 328, luminance low pass filter 10 304, chrominance low pass filter 314, and timing signals from timing generator 308. blueign-to-red signal-to-MAC ).

15

Figure 6 is a diagram of a line memory that can be used to compress or decompress luminance or chrominance. This line memory illustrates memory devices 110a and 110b in Figure 3 and 302 and 312 in Figure 5. The line memory 20 is described as performing decompression of luminance. Fig. 7 is a diagram illustrating the line memory inputs and its outputs during the luminance compression removal operation. The numbers in parentheses are for C or D / 2 MAC embodiments. When the MAC television signal arrives, clock 1 writes 1,125 (1044) luminance samples to line memory 400 at MAC sampling rate 2047.5 (1944) fH · At the same time, clock 2 causes the contents of line memory 402 to be read to the output line at frequency 1365 (1296) fy. During the next video line, 1,125 (1044) luminans-30 samples are written to the line memory 402 at clock 2 operating at 2047.5 (1944) fH. At the same time, • the luminance samples stored in the line memory 400 are read as the clock 1 output line 1365 (1296) fH. A similar function is used to remove chrominance samples from the compression, 35 where the clocks vary between 2047.5 (1944) fH and 682.5 (648) fjj.

18 93069

Although illustrative embodiments of the present invention have been described in detail with reference to the accompanying drawings, it is to be understood that the invention is not limited to these specific embodiments. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention.

Claims (24)

An encoder for converting a television signal containing luminance (Y) and chrominance (RY, BY) information and data information connected to the signal into a B-MAC television signal for later conversion with decoders into a combined television signal, comprising: sampling means (102a-102c, 112a-112d) for sampling the luminance information (Y) at the frequency f and for sampling the chrominance information (R-Y, B-Y) at frequency f2 and for sampling the data information at frequency compression means (110a, 110b, 114) for converting the frequency of luminance and chrominance samples to the frequency f4 and the frequency of the data sample; multiplexing means (118) for combining compressed luminance and chrominance samples as well as data samples for a B-MAC television signal; a master clock (40) for generating a master clock signal of frequency fg and distribution means (402-408) for input of the signals derived from the master clock signal to said sampling means and said compression means at frequencies f f, f2, f3 and f4, characterized by that for the frequencies: f0 = 3f! = 6f2 = 2f4 = 1365 k fH in which k is a positive integer greater than 2 and that f3 is a given constant frequency independent of the value k. 2. Encoder for converting a television signal containing luminance (Y) and chrominance (RY, BY) information and data information connected to the signal into a C, D or D / 2 MAC television signal for later conversion with 25 decoder for a combined television signal, comprising: sampling means (I02a-102c, 112a-112d) for sampling the luminance information at frequency f 2 and for sampling the chrominance information at frequency f2 and for sampling data information at frequency f3, compression means ( 110a, 110b, 114) for converting the frequency of the lumina, nance and chrominance samples to the frequency f4 and the frequency of the data sample; multiplexing means (118) for combining compressed luminance and chrominance samples as well as data samples for a C, D-35 or MAC television signal; a master clock (401) for generating a master clock signal at frequency fg and 28 that for the frequencies: 5 fq = 3f] _ = 6f2 = 2f4 = 1296 k fj in which k is a positive integer greater than 2 and that f3 is a given constant frequency independent of the value k. Encoder according to claim 1 or 2, characterized in that for it it applies k = 3. Encoder according to claim 1 or 2, characterized in that for this it applies k = 4. Encoder according to claim 1, characterized in that the television signal follows audio information, said sampling means sampling the audio information at frequency f3, said compression means converting the frequency of the audio samples, and said multiplexing means combining the compressed audio samples into a television signal B said distribution means for said sampling means inputs a signal derived from the main clock signal at frequency f3, in which f3 = 13 fH. Encoder according to claim 1, characterized in that the television signal follows audio information, said sampling means sampling the audio information at frequency f3, said compression means converting the frequency of the audio samples, and said multiplexing means combining the compressed audio samples into a television signal B said distribution means for said sampling means inputs a signal derived from the main clock signal at frequency f3, in which II · 21 f H · Encoder according to claim 2, characterized in that the television signal follows sound information, said sampling means samples the sound information at frequency f3, said compression means converts the frequency of the sound samples, and said multiplexing means combines the compressed sound samples into a C or D television signal, while said distribution means for said sampling means inputs a signal derived from the main clock signal at frequency f3, in which f3 = 1296 fH. Encoder according to claim 2, characterized in that the television signal follows sound information, said sampling means sampling the sound information at frequency f3, said compression means converting the frequency of the sound samples, and said multiplexing means combining the compressed sound samples 2 to a D / , while said distribution means for said sampling means inputs a signal passed from the master clock signal at frequency f3, in which f3 = 648 fH. Encoder according to claim 1, characterized in that for it it applies 30 f0 = 4095 fH ίχ = 1365 fH f 2 = 682.5 f j f4 = 2047.5 fH. Encoder according to claim 2, characterized in that for it it applies to 9,969 f0 = 3888 fH f] = 1296 fj f2 = 648 fH 5 f4 = 1944 fH. Encoder according to claim 1, characterized in that it applies to 10 f (3 = 5460 fh fx = 1820 fH f2 = 910 fH f4 = 2730 fH. Encoder according to claim 2, characterized in that for it it applies f0 = 5148 fH £ λ = 1728 fH 20 f2 = 864 fj f4 = 2592 fH. A decoder for converting a 525-line B-MAC television signal, in which the luminance and chrominance samples are present at frequency f4 and containing data samples, into a combined television signal, comprising: demultiplexing means for separating luminance and chrominance samples from the B-MAC television signal; decompression means for converting the frequency of the separated luminance samples to the frequency f1, for converting the separated chrominance samples to the frequency f2, and for converting the separated data samples to the frequency £ 3; color modulation means for modulating the auxiliary carrier path with the compressed chrominance samples; Output means for combining the decompressed luminance samples and the modulated auxiliary carrier path into a combined one. television signal and for delivering the decompressed data samples to be connected to the combined television signal, a master clock for generating a master clock signal at the frequency fo; And distribution means for input of signals into said decompression means and said color modulation means at frequencies £, £, 2, £ and och 4 distributed from the main clock signal; Characterized in that for the frequencies: fq = 3f 1 = 6f2 = 2f4 = 1365 k fj in which k is a positive integer greater than 2 and f3 is a predetermined constant frequency independent of the value k. A decoder for converting a C, D or D / 2 MAC telecommunication signal, in which the luminance and chrominance samples are present at frequency f4 and data samples at frequency f3, into a combined television signal comprising: demultiplexing means for separating the luminance, chrominance, and data samples from the C, D, or D / 2 MAC television signal; . Decompression means for converting the frequency of the separated luminance samples to the frequency for converting the separated chrominance samples to the frequency f2 and for converting the separated data samples to the frequency f3; color modulating means for modulating the auxiliary carrier path with the decompressed chrominance samples; ·; output means for combining the decompressed luminance samples and the modulated auxiliary carrier into a combined television signal and for delivering the decompressed data samples to be connected to the combined television signal; a master clock for generating a master clock signal at the frequency fo; and distribution means for inputting signals derived from the master clock signal in said decompression means and said color modulation means at frequencies ff2, f3 and f4; characterized in that for the frequencies: 5 fq = 3f2 = 6f2 = 2f4 = 1296 k fj in which k is a positive integer greater than 2 and £ 3 is a predetermined constant frequency independent of the value k. Decoder according to Claim 13 or 14, characterized in that for k = 3. Decoder according to claim 13 or 14, characterized in that for this it applies k = 4. Decoder according to claim 13, characterized in that said B-MAC television signal contains audio samples, said de-multiplexing means separates the sound samples from the B-MAC television signal, said decompression means changes the frequency of the sound sample to said frequency δ the output means outputs the decompressed audio samples to accompany the combined television signal, said distribution means supplying in said decompression means a signal passed from the main clock signal at the frequency £ 3, in which f3 = 13 f H · Decoder according to claim 13, characterized in that said B-MAC television signal contains audio samples, said multiplexing means separates the sound samples from the B-MAC television signal, said decompression means changes the frequency of the sound sample to the frequency £ 3. said output means outputs the decompressed audio samples to accompany the combined television signal, said distribution means. feeds in said decompression means a signal passed from the main clock signal at frequency f3, in which 33 9όϋ69 f 3 = 21 fH · Decoder according to claim 14, characterized in that said C or D-MAC television signal contains audio samples, said demultiplexing means separates the sound samples from the C or D-MAC television signal, said decompression means changes the frequency of the sound sample to the frequency £ 3. said output means outputs the decompressed audio samples to accompany the combined television signal, said distribution means in said decompression means transmits a signal passed from the main clock signal at frequency £ 3, in which f3 = 1296 fH. 15 Decoder according to claim 14, characterized in that said D / 2 MAC signal contains sound samples, said demultiplexing means separates the sound samples from the D / 2 MAC television signal, said decompression means changes the frequency of the sound sample to the frequency £ 3, and said output means outputs the decompressed audio samples to accompany the combined television signal; said distribution means in said decompression means feeds a signal passed from the main clock signal at frequency £ 3, in which 25 t £ 3 = 648 fj. Decoder according to claim 13, characterized in that for it it applies 30 fn = 4095 fH it w 11 f! = 1365 fH f2 = 682.5 fj f4 = 2047.5 fH. 35 Decoder according to claim 14, characterized in that it applies to 93069 34 f0 = 3888 fH fx = 1296 fH f2 = 648 fH f4 = 1944 fH. 5 Decoder according to claim 13, characterized in that for it it applies fg = 5460 fj 10 = 1820 fH f2 = 910 fH f4 = 2730 fH. Decoder according to claim 14, characterized in that for it it applies f0 = 5184 fH fx = 1728 fH f2 = 864 fH 20 f4 = 2592 fH. II